Operations and Maintenance Manual Plumbing Description
Version 1.2 - June 2004 7 - 5
VACUUM SYSTEM
Refer to the engineering drawings labeled 118168P_ (pneumatic) and 118168A_
(assembly) as well as the Pneumatic Adjustments chapter of this manual for details on
vacuum use and related valve panels.
The vacuum system controls the vacuum source needed to secure the wafers to the
work chucks, the spin-rinse station, the pre-aligner, and the robot end effector. The
inhouse vacuum source, which enters from the rear of the machine, must be an average
of 22 inches of mercury.
Normally open valves are used on all wafer chucks to prevent the release of wafers in
the event of a loss of power. When the solenoid of a wafer valve is de-energized, air
pilot pressure forces the valve's diaphragm down to divert vacuum to the cylinder port.
Air pilot pressure must be available to move the diaphragm. When the solenoid is
energized, the air pilot source is cut off, allowing the spring to return the diaphragm
and close off the vacuum source. Analog vacuum sensors on the work chucks and
spin-rinse station and vacuum switches on the pre-aligner and robot test to see if
vacuum is in the line, indicating that a wafer is attached. Whenever a solenoid is de-
energized to release a wafer, the blow-off solenoid energizes, routing air into the
vacuum lines to release the grip upon the wafer (excluding the pre-aligner which is
vented to atmosphere).
The vacuum connection to the machine will collect a significant amount of process
water and silicon particles through the vacuum line to the vacuum source. An isolated
vacuum pump with a self-contained drain system is available from Strasbaugh as a
machine option. For use with a facility vacuum supply, a wall-mountable
vacuum/waste separator is also available.
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